Reed-blown wind instruments include the clarinet, saxophone, oboe and bassoon. In single reed instruments such as the saxophone and clarinet, a vibrating plate, clamped to the mouthpiece, sets up a standing wave in the barrel of the instrument, and the frequency of these waves is controlled by the musician. The vibrating plate is called the reed, and it is normally made of a natural cane material. The musician creates the vibration by blowing into the gap between the reed and the mouthpiece, which creates and maintains a standing wave in the barrel of the instrument. In the oboe and bassoon, a double reed is used.
Natural cane is the preferred material for the construction of reeds. Apparently, the material properties of natural cane are ideal for the construction of reeds, and reeds made of this material are generally acknowledged to be superior to those made of other materials. Nevertheless, natural cane reeds have many disadvantages. Because the material comes from a natural source, there is a variation in material properties which results in a variation in playing characteristics. Thus, not every reed purchased will be found suitable for playing. Secondly, the reed is hygroscopic, and must be extensively conditioned by exposing it to water prior to playing. Thirdly, cane is prone to splitting along the grain, which causes the reed to become unplayable. Fourthly, the reed material gradually breaks down under the influence of high frequency, low amplitude fatigue to which it is subjected.
As a result of these deficiencies, many inventors have proposed modifications of the reed structure. There have been three basic approaches to produce improved reeds: treatment of natural cane, alternative materials, and alternative materials together with a modified reed configuration.
There is considerable uncertainty in the literature regarding the material properties and configuration required to produce acceptable tonal quality. As a result, in one approach, discussed in U.S. Pat. Nos. 3,340,759, 3,705,820 and 4,145,949, synthetic coatings and penetrating resins are used on the natural cane reed to improve its resistance to water and its durability. Not all of the deficiencies of natural cane are addressed through these methods, however, and so alternative materials and reed configurations have been proposed.
The second principle method of creating an improved reed is to use a material with properties similar to those of cane. However, there is considerable confusion in the literature as to which material and structural properties are important. U.S. Pat. No. 3,420,132 suggests that the stiffness, density and viscous damping are the important material properties, and also discusses several features of the configuration that control the sound quality. U.S. Pat. No. 3,759,132 cites the properties of wet cane, suggesting that these are more important than the properties of dry cane. In U.S. Pat. No. 3,905,268 the ratio of elastic modulus/mass is cited as being important. Furthermore, U.S. Pat. No. 4,355,560 suggests that the individual modulus and density need not be similar to those of cane, provided the ratio of modulus to density (termed the "acoustic impedance") is similar to that of cane. U.S. Pat. No. 4,014,241 suggests that elastic modulii both transverse and parallel to the long axis of the reed are important. The importance of viscous damping is discussed in U.S. Pat. Nos. 3,420,132, 4,337,683, and 5,542,331, but many other patents ignore this property. In U.S. Pat. No. 5,542,331, a means of controlling damping through the inclusion of special damping materials such as hollow fibres is disclosed. U.S. Pat. No. 5,227,572 suggests that the tone of a titanium reed can be controlled by heat treatment to alter the hardness. In this same patent, the failure of previous metal reeds to simulate the "fibratory response of cane" was attributed to the "ductal nature of the metal".
The preceding discussion indicates that there is considerable confusion in the art about the important properties of cane for reproducing the tonal qualities of a natural cane reed.
None of the polymers known in the art with a density sufficiently low to match that of either wet or dry cane have an elastic modulus which is as high as that of either wet or dry cane in the fibre direction. For example, isotropic polypropylene, with a density of approximately 0.91 g/mL, has an elastic modulus of approximately 1.0 to 1.6 GPa, less than one third the modulus of cane. Polymer-composite materials having sufficient modulus, such as carbon fibre reinforced epoxy, generally have higher densities, as do all metals. In fact, U.S. Pat. No. 3,759,132 teaches that common plastics are unsuitable because of their low modulus and relatively high density, and that composite materials such as glass fibre reinforced plastic are difficult to use because they tend to split. A review of a broad materials database such as the database found in the Cambridge Materials Selector (Cambridge Materials Selector, Version 2.02, Granta Design, Cambridge, U.K.) reveals that there are no commonly available polymers, metals, ceramics or composites with comparable elastic modulus and density to that of wet or dry cane. The density of polymers and composites can be reduced by inclusion of hollow elements, such as hollow glass microballoons. For example, U.S. Pat. No. 4,337,683 proposes the use of graphite/epoxy composite ribs spaced with epoxy/microballoon composite regions to achieve the desired bending stiffness and mass for the reed. U.S. Pat. No. 3,759,132 suggests the use of metal ribs spaced with low density material for the same purpose. However, U.S. Pat. No. 3,420,132 teaches that the last 1/4 to 3/8 of an inch of the very tip of the reed controls the elastic response. In this region, the tip may be as thin as 100 .mu.m (100 micrometers or 0.004"), and hence complicated ribbed or shaped structures are very difficult to obtain in a reproducible way.
Many investigators consider the linear mass distribution and overall bending stiffness to be more important than the modulus and density of the material used to manufacture the reed, leading to the third principle method of creating an improved reed. These investigators have suggested an overall reed shape which is different to that of the conventional reed in order to deliver the required bending stiffness and mass distribution. Even with materials of low modulus and/or higher density than cane, the bending stiffness to mass ratio can be made equivalent to that of a cane reed by an increase in the cross-sectional moment of inertia. For example, U.S. Pat. No. 3,905,268 suggests an arched transverse cross-section with longitudinal ridges to produce a higher moment of inertia than that of the conventional cane reed cross-section. In U.S. Pat. No. 4,014,241, a multitude of longitudinal channels are used in a synthetic material, in order to match both the longitudinal and transverse bending stiffness of a cane reed. Cane is anisotropic, with a longitudinal modulus substantially greater than the transverse modulus.
The failure of these patents to reveal an ideal synthetic reed is clearly evidenced by the relative scarcity of such products in the commercial market and the widespread preference among accomplished musicians for conventional cane reeds. Clearly the vibration modes are so complex that attempts to produce acceptable reeds with nonstandard cross-sectional shapes have failed to produce a reed which satisfactorily mimics the behaviour of the natural cane reed. Complex geometries and materials combinations are very difficult to achieve in the extremely thin tip of the reed that apparently dominates the vibration response.